Membrane diffusion devices are used for a variety of purposes, particularly for the dialysis or oxygenation of blood, in the first instance to remove toxic waste products from the blood in the manner of an artificial kidney, and in the second instance to function as an artificial lung.
There are two major classes of membrane diffusion devices: the first class is the coil type diffusion device in which a long, tubular diffusion membrane is wrapped in a coil with membrane support material to provide a long blood flow path through the tubular membrane of the device. An example of this is the well-known coil dialyzer manufactured by Travenol Laboratories, Inc. of Deerfield, Illinois.
The second major type of diffusion device is the flat plate type in which flat sheets of membrane are placed alternatingly in a stack between flat membrane support members. The blood flow path through this second device is relatively short, but a large number of separate blood flow paths are provided in parallel arrangement when a high capacity diffusion device is desired. An example of this device is the Kiil dialyzer.
Both of these major types of diffusion devices have their respective advantages and disadvantages. A chief advantage of the coil dialyzer is the long blood flow path, which permits complete diffusion for the blood or other material to which the diffusion device is to be applied. Hence, coil dialyzers provide an excellent clearance of urea, creatinine and the other waste products from the blood.
The flat plate type diffusion devices, however, may be compact, and can have a high flow capacity. Furthermore, dialyzers made in accordance with this design are more readily used with the "single pass" technique of passing dialysis solution through the device and then disposing of it, rather than recirculating part of the spent dialysis solution, as is typically done with coil type dialyzers. However, because of the relatively short blood flow path through the flat plate type diffusion devices, their capacity to remove the unwanted waste products from the blood (or other material desired to be processed) is restricted, because of too short a fluid transit time and ordinary membrane-solute diffusion resistance.
In accordance with this invention, a diffusion device is provided which combines the advantages of the coil type diffusion device with the flat plate type diffusion device, in that a long blood flow path is provided in a flat plate diffusion device by a technique which is readily capable of commercial use. Furthermore, by this invention, essentially the same design of flat plate diffusion device can be easily modified to provide a blood flow path, as well as a dialysis solution or oxygen flow path, which can be of any desired length and flow capacity, with only very simple modification of the assembly process of the dialyzer of this invention.
Furthermore, in accordance with this invention, a novel membrane support plate design is disclosed which provides improved sealing and manifolding of fluid into and out of the diffusion device.